This invention relates to a metallic reinforcing cord structure and more particularly to such structure suitable for reinforcing elastomeric articles such as pneumatic tires, reinforced hoses and the like.
Metallic reinforcing cord structures of the type herein disclosed have long been known in the art. They are conventionally utilized in pneumatic vehicle tires, and more particularly in the breaker structures of such tires, in conveyor and drive belts and in high pressure hoses. Clearly therefore, it is advantageous for such reinforcing cord structures to have certain properties, such as a high compression modulus which increases resistance to buckling and fatigue failure, and to be highly adherent to the elastomeric material in which the reinforcing cord structure is embedded.
Representative examples of reinforcing cord structures known in the prior art are exemplified by U.S. Pat. No. 3,336,744 and U.S. Pat. No. 3,032,963. U.S. Pat. No. 3,336,744 to Peene illustrates a metallic reinforcing cord structure including two interior core wires, six exterior wires symmetrically disposed about the two core wires, the diameter of the outer wires being between about 1.7 and about 2 times the diameter of the cores wires and a single wire helically wrapped about the six outer wires for the purpose of improving the adherence of the cord structure to the material in which it is embedded. This structure has been found to be not completely satisfactory without the inclusion of a helically wrapped filament about the outer wires, the wrapping of which filament requires an expensive and complex process, both because its compression would not be sufficiently high for use in high stress environments such as, for example, in pneumatic vehicle tires which must be able to withstand repeated tension, compression and bending stresses and further because the adhesion between the reinforcing cord structure and the elastomeric material in which it is embedded would be insufficient if the cord structure were wrapped closely enough to render it stable without utilizing the expedient of the helical wrap. U.S. Pat. No. 3,032,963 to Fenner discloses a cord structure in which three equal diameter wires in a triangular configuration are used to form the core of the cord and six equal diameter wires are symmetrically disposed about the core, the diameter of each of the outer wires being approximately twice that of each of the core wires. This structure has also been found to be not completely satisfactory because the compression modulus of the structure is lower than that required by high compression stress uses.